Repeat use data inserting apparatus and digital broadcast transmitting system

ABSTRACT

A repeat use data inserting apparatus for repeatedly inserting repeat use data into program data in accordance with appropriate timings. The apparatus comprises a data holding unit and a data multiplexing unit. The data holding unit holds the repeat use data made of a plurality of material data in the form of separately encoded streams. The data multiplexing unit multiplexes separately encoded streams of a plurality of material data constituting the program data during a period other than a data insertion period during which the repeat use data is inserted into the program data. The data multiplexing unit further inserts repeatedly the repeat use data into the program data during the data insertion period by multiplexing the separately encoded streams of the plurality of material data constituting the repeat use data held in the data holding unit.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a repeat use data insertingapparatus for inserting repeat use data into program data in accordancewith appropriate timings, as well as to a digital broadcast transmittingsystem which comprises the repeat use data inserting apparatus and whichtransmits a unified stream of program data and repeat use data preparedby the repeat use data inserting apparatus.

[0002] Recent years have seen the commercialization of multi-channeldigital broadcasting systems using advanced digital compressiontechniques to transmit numerous channels of program data in a singledata stream. The multi-channel digital broadcasting system needs to havethe capability of repeatedly inserting so-called repeat use data intoeach of a plurality of channels of program data in accordance withsuitable timings. In the context of this specification, repeat use datarefers to repeatedly used data during broadcast such as news clips andcommercial messages.

SUMMARY OF THE INVENTION

[0003] It is an object of the present invention to provide a repeat usedata inserting apparatus and a digital broadcast transmitting systemusing the apparatus, whereby the storage capacity and transfer rate forrepeat use data are reduced, the process for changing time baseinformation is eliminated, momentary interruption of video or audio datais averted, and generation of noise is suppressed.

[0004] One aspect of the present invention provides a repeat use datainserting apparatus for repeatedly inserting repeat use data intoprogram data in accordance with appropriate timings, and a digitalbroadcast transmitting system for use with that apparatus, the repeatuse data inserting apparatus comprising: data holding means for holdingthe repeat use data made of a plurality of material data in the form ofseparately encoded streams; and data multiplexing means for multiplexingseparately encoded streams of a plurality of material data constitutingthe program data during a period other than a data insertion periodduring which the repeat use data is inserted into the program data, thedata multiplexing means further inserting repeatedly the repeat use datainto the program data during the data insertion period by multiplexingthe separately encoded streams of the plurality of material dataconstituting the repeat use data held in the data holding means.

[0005] In the repeat data inserting apparatus and digital broadcasttransmitting system of the invention, the repeat use data is held by thedata holding means in the form of separately encoded stream of theplurality of material data. In that setup, during a period other thanthe data insertion period, the data multiplexing means multiplexes theseparately encoded streams of the plurality of material dataconstituting the program data. During the data insertion period, thedata multiplexing means multiplexes the separately encoded streams ofthe plurality of material data constituting the repeat use data held inthe data holding means.

[0006] The program data and the repeat use data are multiplexed asdescribed, and so are the separately encoded streams constituting thematerial data. As a result, a bit stream of repeat use data isrepeatedly inserted into a bit stream of program data, whereby a unifiedstream of data is acquired.

[0007] Other objects and further features of the invention will beapparent from the following detailed description when read inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008]FIG. 1 is a block diagram of a repeat use data inserting apparatusand a digital broadcast transmitting system embodying the invention;

[0009]FIG. 2 is a conceptual view showing how program data are typicallysubjected to multiplexing and separating processes;

[0010]FIG. 3 is a schematic view sketching how program data and repeatuse data are multiplexed;

[0011]FIG. 4 is a block diagram showing how encoder-multiplexers and aserver are illustratively configured;

[0012]FIG. 5 is a schematic view of a data storage structure in a harddisk array;

[0013]FIGS. 6A, 6B and 6C are views of typical file structures forcommercial data;

[0014]FIG. 7 is a flowchart of steps in which a multiplexing controlleroperates illustratively;

[0015]FIG. 8 is a flowchart of steps in which a disk controller operatesillustratively;

[0016]FIG. 9 is a view of a typical commercial list;

[0017]FIG. 10 is a schematic view showing the storage capacity of anFIFO memory unit;

[0018]FIGS. 11A, 11B and 11C are schematic views showing how video dataheld in the FIFO memory unit vary;

[0019]FIG. 12 is a block diagram of a system adopting ahitherto-proposed arrangement for inserting repeat use data into programdata; and

[0020]FIG. 13 is a block diagram of a system adopting anotherhitherto-proposed arrangement for inserting repeat use data into programdata.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] A repeat use data inserting apparatus and a digital broadcasttransmitting system both embodying the invention will now be describedin detail with reference to the accompanying drawings.

[0022] So far, repeat use data is inserted into program data through theuse of one of two data inserting arrangements proposed as follows: thefirst arrangement involves having repeat use data not compressed uponinsertion into the program data. The second arrangement requires thatrepeat use data be subject to compressed encoding and multiplexingbefore being inserted into program data.

[0023]FIG. 12 is a block diagram of a multi-channel digital broadcastingsystem adopting the first arrangement for inserting repeat use data intoprogram data.

[0024] The multi-channel digital broadcasting system of FIG. 12comprises a digital broadcast transmitting system 100 installed in abroadcasting center, a communication satellite 200 for relayingtransmitted data from the digital broadcast transmitting system 100, anda digital broadcast receiving system 300 installed in each viewer'shousehold to receive the data relayed by the communication satellite200.

[0025] The digital broadcast transmitting system 100 has N video taperecorders (VTRs) 110(1) through 110(N) for N channels (N is an integerof at least 2), a changeover switch 120, N encoder-multiplexers 130(1)through 130(N) for the N channels, a multi-channel developing unit 140,a transmitting antenna 150, and a server 160 for managing uncompressedrepeat use data. Each digital broadcast receiving system 300 includes areceiving antenna 310 and a receiving terminal 320.

[0026] In the setup above, during a period where repeat use data isinserted into n (n=1−N) channels of program data (the period is called adata insertion period), uncompressed repeat use data from the server 160is fed through the changeover switch 120 to the correspondingencoder-multiplexers 130(n). During a period other than the datainsertion period (called a data noninsertion period), the program datafrom as many as n VTRs 110(n) for n channels are supplied through thechangeover switch 120 to the encoder-multiplexers 130(n).

[0027] The data fed to the encoder-multiplexers 130(n) are compressedand encoded in terms of individual material data types (video data,audio data, etc.) before being multiplexed. The compression, encodingand multiplexing processes are implemented illustratively on the basisof MPEG (Moving Picture Experts Group) 2 specifications.

[0028] Multiplexed outputs comprising N channels of data are developedinto multiple channels by the multi-channel developing unit 140 beforebeing transmitted via the transmitting antenna 150. The transmitted datais relayed by the communication satellite 200 and received by thereceiving antenna 310. The receiving terminal 320 separates data of adesired channel from the received data, decodes the separated output andreproduces the decoded data.

[0029]FIG. 13 is a block diagram of a multi-channel digital broadcastingsystem adopting the second arrangement for inserting repeat use datainto program data.

[0030] The system of FIG. 13 includes a digital broadcast transmittingsystem 400, a communication satellite 500 and a digital broadcastreceiving system 600. The digital broadcast transmitting system 400comprises VTRs 410(1) through 410(N), a changeover switch 420,encoder-multiplexers 430(1) through 430(N), a multi-channel developingunit 440, a transmitting antenna 450, and a server 460 for managingrepeat use data. The digital broadcast receiving system 600 has areceiving antenna 610 and a receiving terminal 620.

[0031] In the system of FIG. 13, the server 460 manages the repeat usedata that are encoded and multiplexed. That is, the server 460 managesthe repeat use data in the form of an MPEG2-based final bit streamcalled a transport stream. The repeat use data are fed to themulti-channel developing unit 440 during the data insertion period on nchannels, to be multiplexed with the n channels of program data.

[0032] The above-described two arrangements for inserting repeat usedata into program data have the following problems:

[0033] (1) The first arrangement uses uncompressed repeat use data. Thisamounts to an enormous quantity of repeat use data that must beaccommodated by a storage medium of a sufficiently large capacity.

[0034] Generally, individual repeat use data items are limited inquantity. On the other hand, a multi-channel broadcast setup typicallyrequires having about 1,000 items of repeat use data stored in thestorage medium dedicated to such data. The total amount of repeat usedata to be stored is huge even though the individual data items aresmall. Thus the first arrangement for inserting repeat use data intoprogram data requires the use of a storage medium of a considerablylarge capacity.

[0035] Furthermore, the first arrangement above requires establishingfor repeat use data a transfer rate high enough to cover all channels.The reason for this is that it is sometimes necessary to broadcastdifferent commercial messages and news clips simultaneously on allchannels. Thus the first arrangement for repeat use data insertionrequires the use of a high-speed storage medium for holding repeat usedata.

[0036] (2) The second arrangement for inserting repeat use data intoprogram data involves having repeat use data compressed for storage.This means that the storage medium for accommodating repeat use data maybe small in capacity and that the transfer rate for repeat use data maybe lowered. Still, the need to have the repeat use data stored in amultiplexed fashion requires changing time base information (i.e., timemanagement information) whenever the data are inserted into programdata.

[0037] The second arrangement above has another problem. When programdata and repeat use data are switched at a given point in time andtransmitted, the video or audio part of the program can be interruptedmomentarily or can generate noise upon such switchover. This is becausethe multi-channel digital broadcasting system, in an attempt to reducethe capacity of a buffer memory on the part of the receiving system 600,causes the transmitting system 400 to multiplex video data and audiodata using time differences.

[0038]FIG. 1 is a block diagram of a digital broadcast transmittingsystem comprising a repeat use data inserting apparatus, the system andthe apparatus embodying the invention.

[0039] The transmitting system of FIG. 1 comprises VTRs 710(1) through710(N) corresponding to N channels (N is an integer of at least 2) andgenerating program data, encoder-multiplexers 720(1) through 720(N) thatencode and multiplex the program data from the VTRs 710(1) through710(N), a changeover switch 730 that connects the VTRs 710(1) through710(N) with the encoder-multiplexers 720(1) through 720(N), amulti-channel developing unit 740 that develops multiplexed outputs fromthe encoder-multiplexers 720(1) through 720(N) into multiple channels, atransmitting antenna 750 that transmits the multi-channel output fromthe multi-channel developing unit 740, and a server 760 that managesrepeat use data.

[0040] The server 760 manages the repeat use data in the form ofseparately encoded streams (elementary streams) representing a pluralityof material data. The material data constituting the repeat use datatypically include video data and audio data. The material data aregenerally compressed and encoded in accordance with MPEG2specifications.

[0041] The setup above works as follows: during a data noninsertionperiod on n channels (n=1−N), the program data from the VTRs 710(n) forthe n channels are fed via the changeover switch 730 to theencoder-multiplexers 720(n).

[0042] Having reached the encoder-multiplexers 720(n), the program dataare compressed and encoded thereby in terms of individual material datatypes according to MPEG2 specifications. The process provides separatelyencoded streams reflecting the individual material data. Video data andaudio data generally make up the material data constituting the programdata.

[0043] A plurality of separately encoded streams from the datacompression and encoding process above are multiplexed in accordancewith MPEG2 specifications. This provides a single stream that unifiesthe separately encoded streams. The single stream is called a transportstream, one of MPEG2-based packet streams.

[0044] During a data insertion period, the encoder-multiplexers 720(n)are supplied with the separately encoded streams representing aplurality of material data constituting the repeat use data held in theserver 760. The separately encoded streams fed to theencoder-multiplexers 720(n) are multiplexed thereby according to MPEG2specifications. The process provides a single stream (transport stream)that unifies the separately encoded streams.

[0045] As described, the encoder-multiplexers 720(n) for the n channelsmultiplex the program data and repeat use data over the n channels, aswell as the separately encoded streams representing the plurality ofdata constituting the data. In this manner, the process turns programdata bit streams into a single stream into which repeat use data bitstreams are inserted in accordance with predetermined timings.

[0046] In the multiplexing process, time base information is provided inorder to synchronize the video and audio data. The time base informationincludes a decoding time stamp (DTS) indicating when to decode videodata and audio data, a presentation time stamp (PTS) specifying when toreproduce and output the decoded video and audio data, and system clockreference (SCR) as well as program clock reference (PCR) designating theclock reference for decoding, reproduction and output.

[0047] The single stream coming out of the encoder-multiplexers 720(1)through 720(N) for the N channels is developed by the multi-channeldeveloping unit 740 into multiple channels. That is, the unified streamrepresenting the N channels is first multiplexed and then encoded andmodulated in preparation for transmission. The multi-channel output istransmitted via the transmitting antenna 750.

[0048]FIG. 2 is a conceptual view showing a multiplexing and aseparating process dealing with separately encoded streams representinga plurality of material data constituting program data. The setup ofFIG. 2 indicates audio data that is typically composed of two kinds ofaudio data, one in Japanese and the other in English.

[0049] Separately encoded streams ST11 through ST13 representing thethree kinds of material data are multiplexed by the encoder-multiplexers720(n). The process provides a single stream ST20 that unifies the threeencoded streams ST11 through ST13. The unified stream ST20 is laterseparated into the separately encoded streams ST11 through ST13 by areceiving terminal included in the digital broadcast receiving system.The separately encoded streams denoting the repeat use data are alsomultiplexed and then separated in a similar manner, which will not bedescribed further.

[0050]FIG. 3 is a schematic view sketching how program data and repeatuse data are multiplexed. FIG. 3 shows an example in which program datais constituted by movie data and repeat use data is made of commercialdata CM (commercial messages). Furthermore, the movie data comprisesvideo data, audio data in Japanese. and audio data in English; thecommercial data includes video data and audio data in Japanese.

[0051] As shown in FIG. 3, during data noninsertion periods TN(1),TN(2), etc., the separately encoded streams representing the threematerial data constituting the movie data are multiplexed. During datainsertion periods TI(1), etc., on the other hand, the separately encodedstreams representing the two material data constituting the commercialdata are multiplexed. The movie data and commercial data are thusmultiplexed, and so are the separately encoded streams denoting theplurality of material data constituting these data. The processeventually provides a single stream that unifies the separately encodedstreams representing the movie data and the streams representing thecommercial data.

[0052]FIG. 4 is a block diagram showing how the encoder-multiplexers720(n) and the server 760 in FIG. 1 are illustratively configured.

[0053] As shown in FIG. 4, each encoder-multiplexer 720(n) includes avideo encoder 721(n) that compresses and encodes video data VDconstituting the program data from the VTR 710(n), and an audio encoder722(n) that likewise compresses and encodes audio data AD. FIG. 4 showsan example in which one type of audio data AD is furnished.

[0054] The encoder-multiplexer 720(n) further comprises a video first-infirst-out (FIFO) memory unit 724(n) for temporarily accommodating thevideo data VD constituting the repeat use data from the server 760, anaudio FIFO memory unit 725(n) for temporarily holding the audio data ADfrom the server 760, and an FIFO control circuit 726(n) for detectingthe quantity of the remaining data in the FIFO memory units 724(n) and725(n).

[0055] In addition, the encoder-multiplexer 720(n) has a multiplexer727(n) and a multiplexing controller 728(n) that controls themultiplexer 727(n) in operation. The multiplexer 727(n) multiplexes, inaccordance with MPEG2 specifications, two separately encoded streamscoming from the encoders 721(n) and 722(n) and another two separatelyencoded streams from the FIFO memory units 724(n) and 725(n). Themultiplexing controller 728 is implemented illustratively by use of acentral processing unit (CPU).

[0056] The server 760 comprises a hard disk array 761 for holding therepeat use data, and a disk controller 762 for controlling the hard diskarray 761. The disk controller 762 is implemented illustratively by useof a computer.

[0057]FIG. 5 is a schematic view of a data storage structure in the harddisk array 761. The example of FIG. 5 shows repeat use data typicallycomposed of commercial data. As illustrated, the hard disk array 761 hasa file established for each of commercial messages CM(m) (m=1, 2, etc.).

[0058] As shown in FIGS. 6A through 6C, each file accommodating acommercial message CM(m) comprises a video file VF(m) (see FIG. 6A) forstoring video data VD, an audio file AF(m) (see FIG. 6B) for holdingaudio data AD, and a size file SF(m) (see FIG. 6C) for retaining sizedata VSD and ASD.

[0059] The video file VF(m) has the video data VD stored in incrementsof frames. The audio file AF(m) has the audio data AD stored also inincrements of frames. The size file SF(m) contains the size data VSDdesignating video data sizes and the size data ASD specifying audio datasizes, the two types of size data being stored in increments of frames.

[0060] The video data VD and audio data AD are stored in the form ofseparately encoded streams. The size data VSD and ASD, as they arestored, indicate the sizes in effect when the video data VD and audiodata AD were compressed and encoded. The compression and encodingprocess above is carried out illustratively by one of theencoder-multiplexers 720(1) through 720(N) for program data while noprogram data is being compressed or encoded.

[0061] The setup above works as follows: during a data noninsertionperiod for each of n channel, the video data VD constituting the programdata from the VTR 710(n) in FIG. 1 is fed to the video encoder 721(n);the audio data AD also making up the program data is fed to the audioencoder 722(n). The video data VD and audio data AD supplied to theencoders 721(n) and 722(n) are compressed and encoded thereby inaccordance with MPEG2 specifications. The process provides separatelyencoded streams representing the video data VD and audio data AD. Thetwo separately encoded streams are multiplexed by the multiplexer 727(n)into a unified stream (called a transport stream).

[0062] Also during the data noninsertion period for each of the nchannels, the FIFO memory units 724(n) and 725(n) are supplied with theseparately encoded streams representing the video data VD and audio dataVD constituting the commercial data held in the hard disk array 761. Theseparately encoded streams thus transferred to the FIFO memory units724(n) and 275(n), reflecting the video data VD and audio data AD, aremultiplexed by the multiplexer 727(n). The multiplexing process providesa single stream (transport stream) that unifies the two separatelyencoded streams.

[0063] The multiplexer 727(n) is controlled in operation by themultiplexing controller 728(n). The transfer of the separately encodedstreams from the hard disk array 761 to the FIFO memory units 724(n) and725(n) is controlled by the disk controller 762.

[0064]FIG. 7 is a flowchart of steps in which the multiplexingcontroller 728(n) operates illustratively. In the example of FIG. 7, itis assumed that repeat use data is commercial data. How the multiplexingcontroller 728(n) works will now be described with reference to FIG. 7.

[0065] In operation, the multiplexing controller 728(n) first requeststhe disk controller 762 to transfer commercial data (step S101). Inturn, the data constituting the commercial message CM(m) held in thehard disk array 761 is transferred therefrom to the FIFO memory units724(n) and 725(n).

[0066] In the case above, the FIFO memory unit 724(n) is fed with theseparately encoded stream representing the video data VD held in thevideo file VF(m) for the commercial message CM(m); the FIFO memory unit725(n) is supplied with the separately encoded stream representing theaudio data AD held in the audio file AF(m). The data transfer process iscarried out until the storage capacities of the FIFO memory units 724(n)and 725(n) are exhausted. The storage capacities are preset so as toaccommodate data comprising a plurality of commercial messages CM(m).This means that the FIFO memory units 724(n) and 725(n) will hold dataconstituting multiple commercial messages CM(m).

[0067] The multiplexing controller 728(n) then controls multiplexing ofprogram data (step S102). Under control of the controller 728(n), themultiplexer 727(n) multiplexes the separately encoded streams of thevideo data VD and audio data VD compressed and encoded by the encoders721(n) and 722(n).

[0068] More specifically, the multiplexing process is controlled asfollows: the multiplexing controller 728(n) asks the encoders 721(n) and722(n) for size data VSD and ASD representing the sizes of the videodata VD and audio data AD. In response, the encoders 721(n) and 722(n)supplies the multiplexing controller 728(n) with the size data VSD andASD representing a plurality of frames (e.g., 15 frames) of video dataVD and audio data AD.

[0069] Given the size data VSD and ASD about the multiple-frame data,the multiplexing controller 728(n) devises a plan to multiplex the videodata VD and audio data AD. The multiplexing plan is a plan thatspecifies the quantities of video data VD and audio data AD to bemultiplexed and the timings used for such multiplexing. The plan isprovided so that video data VD may be compressed and encoded by avariable-length compression and encoding method. Without such a plan,the multiplexing process would involve unevenly transmitted excesses andshortages of video data VD leading to an imbalance between video data VDand audio data AD.

[0070] The multiplexing plan is established in increments not of asingle frame but of a plurality of frames. This is because the planneeds to be optimized so as to take into consideration changes in datasize per frame.

[0071] On the basis of the multiplexing plan thus devised, themultiplexing controller 728(n) requests the encoders 721(n) and 722(n)to transfer separately encoded streams representing a plurality offrames. At the same time, the multiplexing controller 728(n) requeststhe multiplexer 727(n) to multiplex the plurality of frames ofseparately encoded streams. As a result, the encoders 721(n) and 722(n)output the multiple frames of separately encoded streams in accordancewith the multiplexing plan. These separately encoded streams aremultiplexed by the multiplexer 727(n) according to the multiplexingplan.

[0072] When control over the multiple-frame multiplexing process isterminated, the multiplexing controller 728(n) checks to see if it istime to switch from program data to commercial data (step S103). Thatis, a check is made to see if the starting time of a data insertionperiod has arrived. If the time to switch to commercial data has yet tobe reached, the-multiplexing controller 728(n) goes back to step S102 toresume control over the multiplexing process. In step S102, the nextbatch of multiple frames is subjected to the multiplexing process. Inthis manner, the multiplexing process is allowed to continue undercontrol of the multiplexing controller 728(n) until it is time to switchto commercial data.

[0073] When it is time to switch to commercial data, the multiplexingcontroller 728(n) requests the disk controller 762 to transfer the sizedata VSD and ASD denoting the sizes of commercial data (step S104). Inturn, the multiplexing controller 728(n) is supplied with the size dataVSD about video data and the size data ASD about audio data held in thesize file SF(m) in the hard disk array 761. In this case, too, the sizedata VSD and ASD are furnished in increments of a plurality of frames.

[0074] On the basis of the size data VSD and ASD representing themultiple frames from the disk controller 762, the multiplexingcontroller 728(n) devises a plan to multiplex the plurality of frames ofvideo data VD and audio data AD constituting the commercial data inquestion (step S105).

[0075] In accordance with the multiplexing plan thus provided, themultiplexing controller 728(n) requests the FIFO memory units 724(n) and725(n) to transfer separately encoded streams representing the multipleframes. At the same time, the multiplexing controller 728(n) requeststhe multiplexer 727(n) to multiplex the plurality of frames ofseparately encoded streams. This causes the FIFO memory units 724(n) and725(n) to output the multiple frames of separately encoded streamsaccording to the multiplexing plan. These separately encoded streams aremultiplexed by the multiplexer 727 in accordance with the multiplexingplan.

[0076] When control over the multiple-frame multiplexing process isterminated, the multiplexing controller 728(n) checks to see if theprocessing of one commercial message has ended (step S107). That is, acheck is made to see if the ending time of the data insertion period hasarrived. If the multiplexing process of one commercial message has yetto be terminated, the multiplexing controller 728(n) goes back to stepS104 to resume control over the multiplexing process. The next batch ofmultiple frames is then subjected to the multiplexing process. In thismanner, the multiplexing process is allowed to continue under control ofthe multiplexing controller 728(n) until the processing of onecommercial message comes to an end.

[0077] When the multiplexing process of one commercial message hasended, the multiplexing controller 728(n) returns to step S101. Themultiplexing controller 728(n) again starts controlling the multiplexingprocess of the program data and repeat use data. In like manner, everytime the multiplexing process of one commercial message has ended, thesteps described above are repeated.

[0078]FIG. 8 is a flowchart of steps in which the disk controller 762operates illustratively. How the disk controller 762 works will now bedescribed with reference to FIG. 8.

[0079] The steps in FIG. 8 are carried out every time the diskcontroller 762 receives a commercial data transfer request (output instep S101 of FIG. 7) from the multiplexing controller 728(n). Initially,the disk controller 762 calculates currently available capacities of theFIFO memory units 724(n) and 725(n) on the basis of the remainingcommercial data detected by the FIFO control circuit 726(n)(step S201).If the received transfer request is a first request, the availablecapacities of the FIFO memory units 724(n) and 725(n) should match theirstorage capacities. If the transfer request is a second or a subsequentrequest, the currently available capacities match the data quantity ofthe commercial message CM(m) whose multiplexing process has just beenterminated.

[0080] The disk controller 762 then references a commercial list of then channels to determine the commercial message CM(m) whose data shouldbe transferred from the hard disk array 761 to the FIFO memory units724(n) and 725(n)(step S202). The commercial list is a list thatdesignates the sequence in which commercial messages CM(m) are to beoutput. The list is stored illustratively in an internal memory of thedisk controller 762.

[0081] The disk controller 762 then prepares the data making up thecommercial message CM(n) determined in step S202 by an amount matchingthe available capacities calculated in step S201 (step s203).Specifically, those video data VD and audio data AD that match inquantity the currently available capacities of the FIFO memory units724(n) and 725(n) are read from the video file VF(m) and audio fileAF(m) in the hard disk array 761.

[0082] The disk controller 762 transfers the prepared video data VD andaudio data AD to the FIFO memory units 724(n) and 725(n). This shouldfill the two memory units with data to capacity.

[0083] The disk controller 762 checks to see if a request for thetransfer of size data VSD and ASD (i.e., transfer request output in stepS104 of FIG. 7) is received from the multiplexing controller 728(n)(stepS205). The check is repeated until a transfer request has been sent in.

[0084] With a transfer request received, the disk controller 762transfers to the multiplexing controller 728(n) the size data VSD andASD on the commercial message CM(m) subject to multiplexing (step S206).The transfer is effected every time the size data VSD and ASD are readfrom the size file SF(m) in the hard disk array 761. With each transferrequest received, size data VSD and ASD representing a plurality offrames are transferred. The transfer of size data is continued until nofurther transfer request is received.

[0085] With no further transfer request received, the process oftransferring size data VSD and ASD comes to an end. When the transferprocess is terminated, the disk controller 762 stops its controloperation. Upon receipt of a new request for the transfer of commercialdata from the multiplexing controller 728(n), the steps above are againcarried out.

[0086]FIG. 9 is a view of a typical commercial list for n channels. Thelist in FIG. 9 shows a case in which commercial messages CM(m) numbered1, 2, 3, 4, etc., are sent out in the order of CM(1), CM(2), CM(3),CM(6), CM(4), etc.

[0087]FIG. 10 is a schematic view showing how the FIFO memory unit724(n) is related in terms of storage capacity to the amount of videodata VD to be accommodated thereinto. The video data VD in FIG. 10 arearranged in the same sequence in which the corresponding commercialmessages CM(m) are output. As illustrated, the storage capacity of theFIFO memory unit 724(n) is set to be large enough to hold video data VDrepresenting a plurality of commercial messages CM(m).

[0088]FIGS. 11A through 11C are schematic views showing how video datastored in the FIFO memory unit 724(n) vary. FIG. 11A shows a case inwhich the multiplexing controller 728(n) has yet to issue a request forthe transfer of commercial data. In this case, the FIFO memory unit724(n) has no video data VD stored therein.

[0089]FIG. 11B shows a case in which the multiplexing controller 728(n)has generated a first transfer request. In this case, the FIFO memoryunit 724(n) accommodates illustratively video data VD representing twoentire commercial messages CM(1) and CM(2) and video data VDconstituting part of a commercial message CM(3).

[0090]FIG. 11C shows a case in which the multiplexing controller 728(n)has generated a second transfer request. In this case, the FIFO memoryunit 724(n) is replenished with the amount of data corresponding to thevacancy left when the commercial message CM(1) was read out. Asindicated in FIG. 11C, the memory unit is replenished with video data VDconstituting the rest of the commercial message CM(3) and video data VDrepresenting part of a commercial message CM(6). Now the FIFO memoryunit 724(n) is set illustratively with the video data VD representingthe entire commercial messages CM(2) and CM(3) as well as the video dataVD constituting part of the commercial message CM(6).

[0091] In like manner, every time the multiplexing controller 728(n)generates a transfer request, the data-replenishing operation above iscarried out. This keeps the FIFO memory unit 724(n) filled with videodata. Similar processing, which will not be described further, is alsoperformed on the FIFO memory unit 725(n) for audio data AD.

[0092] As described and according to the embodiments of the inventionabove, repeat use data may be stored as compressed. This feature reducesthe amount of stored repeat use data, which in turn cuts back on thestorage capacity for accommodating the data and lowers the transfer rateat which repeat use data are transferred.

[0093] With the embodiments of the invention, repeat use data may bestored in the form of separately encoded streams yet to be multiplexed.This feature dispenses with circuits for changing time base information,averts momentary interruption of video or audio data of the program, andsuppresses generation of noise.

[0094] The embodiments above multiplex repeat use data by simplyinstalling several additional multiplexers 727(n) for multiplexingprogram data. This arrangement forestalls increases in the scale ofcircuits.

[0095] The embodiments comprise the FIFO memory units 724(n) and 725(n)for buffer use which are fed with repeat use data during the datanoninsertion period. This feature further reduces the transfer rate forrepeat use data. Specifically, the transfer rate of the inventivestructure is reduced to about T1/T2 (T1 stands for repeat use dataoutput time and T2 for program data output time) compared with thesecond arrangement described earlier for inserting repeat use data intoprogram data. This makes it possible to implement the hard disk array761 in the form of a hard disk array of a significantly lower speed thanthe one ordinarily used. In addition, a low-transfer-rate cable such asan RS232C cable may be utilized for data transfer between the server760, which is generally set up in a remote location, and theencoder-multiplexers 720(n).

[0096] Furthermore, the embodiments preserve the size data VSD and ASDacquired when repeat use data are compressed and encoded. This featureeliminates the need for a circuit to detect sizes of repeat use data.

[0097] More specifically, if the size data VSD and ASD about repeat usedata were not retained, it would be necessary to detect the sizes ofthese data by referencing them upon read-out from the hard disk array761. Such a structure would require separately installing a sizedetecting circuit. By contrast, the inventive structure holds the sizedata VSD and ASD obtained upon compression and encoding of repeat data,which makes a size detecting circuit unnecessary. Thus the embodimentshelp simply the entire circuit constitution.

[0098] Where a plan to multiplex repeat use data is to be established,the inventive structure devises the plan on the bases of the size datarepresenting a plurality of frames. This makes it possible to take intoconsideration the changes in data size per frame. The feature permitsproviding a more appropriate multiplexing plan than the ordinary setupof devising a multiplexing plan based on the single-frame size data.

[0099] Although the description above contains many specificities, theseshould not be construed as limiting the scope of the invention but asmerely providing illustrations of the presently preferred embodiments ofthis invention.

[0100] For example, the embodiments above have the FIFO memory units724(n) and 725(n) as well as the FIFO control circuit 726(n)incorporated in each of the encoder-multiplexers 720(n). Alternatively,the incorporated components may be included in the server 760 instead.

[0101] With the above embodiments, the file SF dedicated to size data isfurnished so as to accommodate the size data VSD and ASD about repeatuse data. As an alternative, the size data may be contained in the videofile VF or in the audio file AF.

[0102] The embodiments above comprise a single stage of buffer memoryunits (FIFO memory units 724(n) and 725(n) in the description above) fortemporary storage of repeat use data. Alternatively, two stages ofbuffer memory units may be provided instead, the first stage making up alarge-capacity buffer memory arrangement and the second stageconstituting a small-capacity buffer memory setup.

[0103] Thus it is to be understood that changes and variations may bemade without departing from the spirit and scope of the claims thatfollow.

[0104] The major benefits of this invention may be recapitulated asfollows: according to the repeat use data inserting apparatus or digitalbroadcast transmitting system of the invention, repeat use data arestored as compressed. This feature reduces the amount of stored repeatuse data, which in turn cuts back on the storage capacity foraccommodating the data and lowers the transfer rate at which repeat usedata are transferred.

[0105] According to the repeat use data inserting apparatus or digitalbroadcast transmitting system of the invention, repeat use data arestored in the form of separately encoded streams yet to be multiplexed.This feature dispenses with circuits for changing time base information,averts momentary interruption of video or audio data of the program, andsuppresses generation of noise.

[0106] Also according to the repeat use data inserting apparatus ordigital broadcast transmitting system of the invention, repeat use dataare multiplexed by simply providing some additional means formultiplexing program data. This forestalls increases in the overallscale of circuits.

[0107] According to the repeat use data inserting apparatus or digitalbroadcast transmitting system of the invention, temporary storage meansis provided to accommodate temporarily repeat storage data for eachchannel. During the data noninsertion period, repeat use data aretransferred to the temporary storage means. This feature further lowersthe necessary transfer rate for repeat use data, which makes it possibleto implement the repeat use data holding means in the form of dataholding means of a significantly lower speed than the one ordinarilyused.

[0108] Further according to the repeat use data inserting apparatus ordigital broadcast transmitting system of the invention, repeat use dataare preserved along with their size data. This feature eliminates theneed for a circuit to detect sizes of repeat use data.

What is claimed is:
 1. A repeat use data inserting apparatus forrepeatedly inserting repeat use data into program data in accordancewith appropriate timings, comprising: data holding means for holdingsaid repeat use data made of a plurality of material data in the form ofseparately encoded streams; and data multiplexing means for multiplexingseparately encoded streams of a plurality of material data constitutingsaid program data during a period other than a data insertion periodduring which said repeat use data is inserted into said program data,said data multiplexing means further inserting repeatedly said repeatuse data into said program data during said data insertion period bymultiplexing the separately encoded streams of said plurality ofmaterial data constituting said repeat use data held in said dataholding means.
 2. A repeat use data inserting apparatus according toclaim 1 , further comprising temporary holding means for reading andtemporarily holding the repeat use data from said data holding meansduring a period other than said data insertion period; wherein said datamultiplexing means uses the repeat use data held in said temporaryholding means in place of the repeat use data held in said data holdingmeans.
 3. A repeat use data inserting apparatus according to claim 2 ,wherein said temporary holding means includes: holding means fortemporarily holding said repeat use data; remaining data detecting meansfor detecting the quantity of the repeat use data left in said holdingmeans; and transfer means for transferring the repeat use data from saiddata holding means to said holding means during a period other than saiddata insertion period in accordance with a detection output from saidremaining data detecting means, so that the repeat use data held in saidholding means will reach a predetermined quantity.
 4. A repeat use datainserting apparatus according to claim 1 , further comprising size dataholding means for holding size data about each of said plurality ofmaterial data constituting said repeat use data; wherein said datamultiplexing means multiplexes, on the basis of said size data held insaid size data holding means, the separately encoded streams of saidplurality of material data constituting said repeat use data held insaid data holding means.
 5. A digital broadcast transmitting system forrepeatedly inserting repeat use data into program data so as to unifysaid repeat use data and said program data into one data stream and fortransmitting the unified data stream, said digital broadcasttransmitting system comprising: program data encoding means forseparately encoding a plurality of material data constituting saidprogram data in order to generate the separately encoded streams of thematerial data; data holding means for holding said repeat use data madeof a plurality of material data in the form of separately encodedstreams; and data multiplexing means for multiplexing, during a periodother than a data insertion period during which said repeat use data isinserted into said program data, the separately encoded streams of saidplurality of material data constituting said program data output fromsaid program data encoding means, said data multiplexing means furtherinserting repeatedly said repeat use data into said program data inaccordance with appropriate timings during said data insertion period bymultiplexing the separately encoded streams of said plurality ofmaterial data constituting said repeat use data held in said dataholding means.
 6. A digital broadcast transmitting system according toclaim 5 , further comprising temporary holding means for reading andtemporarily holding the repeat use data from said data holding meansduring a period other than said data insertion period; wherein said datamultiplexing means uses the repeat use data held in said temporaryholding means in place of the repeat use data held in said data holdingmeans.
 7. A digital broadcast transmitting system according to claim 6 ,wherein said temporary holding means includes: holding means fortemporarily holding said repeat use data; remaining data detecting meansfor detecting the quantity of the repeat use data left in said holdingmeans; and transfer means for transferring the repeat use data from saiddata holding means to said holding means during a period other than saiddata insertion period in accordance with a detection output from saidremaining data detecting means, so that the repeat use data held in saidholding means will reach a predetermined quantity.
 8. A digitalbroadcast transmitting system according to claim 5 , further comprisingsize data holding means for holding size data about each of saidplurality of material data constituting said repeat use data; whereinsaid data multiplexing means multiplexes, on the basis of said size dataheld in said size data holding means, the separately encoded streams ofsaid plurality of material data constituting said repeat use data heldin said data holding means.
 9. A digital broadcast transmitting systemaccording to claim 5 , wherein said program data encoding means receivesa plurality of channels of program data and separately encodes each ofsaid plurality of channels of program data; and wherein said datamultiplexing means receives said plurality of channels of program dataencoded by said data encoding means, and multiplexes each of saidplurality of channels of program data with said repeat use data; saiddigital broadcast transmitting system further comprising multi-channeldeveloping means for developing into multiple channels sad plurality ofchannels of multiplexed outputs from said data multiplexing means.